Pipettes used for liquid dosage in laboratories typically comprise a piston movable in a cylinder for aspiration of liquid into a tip connected with the cylinder. Such pipettes comprise an elongated handle held by palm grip. The volume is usually adjustable. Usually, there is also a mechanism for removing a used tip from the pipette. There also multichannel pipettes comprising, e.g., eight channels in a row. In manual pipettes, all of the operations are carried out by hand force. The piston in almost all manual pipettes is moved by pushing with thumb a spring loaded rod placed at the upper end of the pipette. Volume is usually set by rotating the knob. The detachable tip is removed by pushing a spring loaded push button at the side of the handle.
There are also electronic pipettes in which the piston is actuated by means of an electric motor and a control system associated with it. The tip removal mechanism is still often manual, but there are also electronic pipettes in which also the tip removal mechanism is electrically driven. There are also electronic pipettes in which pistons are actuated by manual force and which comprise an electronic display only. Electronic pipettes have a user interface for selection of the desired pipetting function (e.g., direct or reverse pipetting), setting of the volume and for giving commands for performing operations. The user interface has the necessary switches for input of the necessary settings and performance of the functions. The user interface is connected to a display, by means of which the volume and other necessary data can be displayed. The display can also show menus allowing data input in the control system.
Manual pipettes are described, e.g., in EP 112 887 and electronic pipettes, e.g., in EP 1 725 333. An example of an electronic pipette is Finnpipette® Novus Electronic Pipette (Thermo Fisher Scientific Oy, Finland). This pipette contains also a counter which counts the total number of pipetting operations after the latest calibration. The use may go and check that number and consider whether recalibration is appropriate. After the recalibration, the counter is automatically reset.
High reliability and safety level are important factors in pipetting. A typical user in a laboratory may have to make hundreds of repetitive pipetting series during a working day. The possibility of pipetting errors, e.g., wrong well in a microplate or wrong volume, exists. Pipetting needs also often very accurate movements when liquid is taken from and dispensed into small vessels. This visual task causes extra workload.